WP User Groups <= 2.1.0 - Cross-Site Request Forgery

The WP User Groups plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 2.1.0. This is due to missing or incorrect nonce validation on the save_terms_for_user and handle_bulk_actions functions. This makes it possible for unauthenticated attackers to perform otherwise restricted administrative actions like putting users into groups via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.